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A little tangent, but still on the topic of attenuators and might make you think.There is another approach to volume control. It involves building the optimal gain structure into your system so that very little attenuation is needed for your typically listening, just enough so that your loud rocking sessions have enough volume at max volume setting. When very little attenuation is used, the attenuator influences are minimized. I hypothesize that it is our infatuation with having 3/4 more to go on the volume dial that causes so much of the sonic degredation from the volume control and why audiophiles are long after the perfect attenuator.This approach is one I hope to eventually build up to but it takes discipline and thinking/planning. The idea is to determine what sources you will use, the less sources the easier. Say we have two sources, a CD player and TT. This is DIY afterall, so effort should be taken to make the two sources have roughly the same voltage output at max output. Then pull out your quietest recordings and your loudest recordings. Note how much attenuation differences is needed between the two. Determine the loudest you'd ever want to listen and the quiestest. Now do some figuring to determine range of control needed.When you have done all the math, you can build your preamp/amp gain stages so that there is just enough headroom to get where you want on the loud times or quiet recordings and not much if any more. Then the average listening is only using a bit of attenuation and you aren't burning up a bunch of current/voltage in the VC which will minimize any affect the attenuator has on the sonics. Essentially, this is a loosened up and more pratical implementation of the no volume control system. I've seen some people profess to use no attenuator, either then voltage divide to get the level they want (which is just a one step attenuator) or they build the gain structures so that it gets there without the voltage division. The latter is much more ideal and is closer to what I am suggesting. The rub is that this allows for no variation in volume to account for variation in recording levels. My music collection has some range, so I'd want some variation. Also some variation is wanted for moods. So we just build in enough gain into the system that allows us enough range but not too much extra that we are back to where we started.If the Squeezebox were my only source, I'd build my amps with no volume control and just enough gain so that a tiny bit of attenuation in the SB would give me the range I needed. But I have multiple sources as do many.
I wonder if you could achive the no attenuation plus have the added option of some more gain? Something like removing some devices from the signal path?
another interesting approach is putting the attenuator after the gain stage. Most preamps put the switches before the gain stage.
Quote from: Mike B. on 7 Jan 2009, 05:29 pmanother interesting approach is putting the attenuator after the gain stage. Most preamps put the switches before the gain stage. Interesting yes, but not without problems. It raises the Zout of your preamp, maybe substantially. Your preamp needs even a lot more drive then before to overcome cables and input capacitance of amp. Not sure what it really buys you.If you place gain > VC > buffer, or buffer > VC > gain, then I can see the worth.
....If you place gain > VC > buffer, or buffer > VC > gain, then I can see the worth.
Quote from: JoshK on 7 Jan 2009, 06:47 pm....If you place gain > VC > buffer, or buffer > VC > gain, then I can see the worth.From a noise perspective, wouldn't the first be prefferable to the later, if |gain| > 1 ?
